c is instance of C
c can be cast to A
ob now refers to d
ob is instance of D
ob now refers to c
ob cannot be cast to D
ob can be cast to A
a
may
be
cast
to
Object
b
may
be
cast
to
Object
c
may
be
cast
to
Object
d
may
be
cast
to
Object
The instanceof operator isn't needed by most programs, because, generally, you know
the type of object with which you are working. However, it can be very useful when you're
writing generalized routines that operate on objects of a complex class hierarchy.
strictfp
A relatively new keyword is strictfp. With the creation of Java 2, the floating-point computation
model was relaxed slightly. Specifically, the new model does not require the truncation of
certain intermediate values that occur during a computation. This prevents overflow or
underflow in some cases. By modifying a class or a method with strictfp, you ensure that
floating-point calculations (and thus all truncations) take place precisely as they did in
earlier versions of Java. When a class is modified by strictfp, all the methods in the class
are also modified by strictfp automatically.
For example, the following fragment tells Java to use the original floating-point model
for calculations in all methods defined within MyClass:
strictfp class MyClass { //...
Frankly, most programmers never need to use strictfp, because it affects only a very small
class of problems.
Native Methods
Although it is rare, occasionally you may want to call a subroutine that is written in a
language other than Java. Typically, such a subroutine exists as executable code for the CPU
and environment in which you are working--that is, native code. For example, you may
want to call a native code subroutine to achieve faster execution time. Or, you may want to
use a specialized, third-party library, such as a statistical package. However, because Java
programs are compiled to bytecode, which is then interpreted (or compiled on-the-fly) by
the Java run-time system, it would seem impossible to call a native code subroutine from
within your Java program. Fortunately, this conclusion is false. Java provides the native
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